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Вы можете ознакомиться и скачать презентацию на тему JavaScript. Доклад-сообщение содержит 29 слайдов. Презентации для любого класса можно скачать бесплатно. Если материал и наш сайт презентаций Mypresentation Вам понравились – поделитесь им с друзьями с помощью социальных кнопок и добавьте в закладки в своем браузере.

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Lecture 8 JavaScript Senior-Lecturer: Sarsenova Zh.N.

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Which one is legal?

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For Loop A loop is a block of code that allows you to repeat a section of code a certain number of times, perhaps changing certain variable values each time the code is executed.

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Why loops are useful? Loops are useful because they allow you to repeat lines of code without retyping them or using cut and paste in your text editor. They save time and trouble of repeatedly typing the same lines of code, but also avoids typing errors in repeated lines. You are also able to change one or more variable values each time the browser passes through the loop.

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$For loop for (initial_expression; test_exp; change_exp) { statements; } One of the most used and familiar loops is the for loop. It iterates through a sequence of statements for a number of times controlled by a condition. The change_exp determines how much has been added or subtracted from the counter variable.$

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For loop for (initial_expression; test_exp; change_exp) { statements; } One of the most used and familiar loops is the for loop. It iterates through a sequence of statements for a number of times controlled by a condition. The change_exp determines how much has been added or subtracted from the counter variable.

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For loop

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For loop Example <script type=“text/javascript”> var counter; for (counter = 1; counter <= 10; counter++) { document.write(counter*counter + “ “); } </script> Display the square of numbers Output: 1 4 9 16 25 36 49 64 81 100

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While loop A while loop just looks at a short comparison and repeats until the comparison is no longer true. The while loop begins with a termination condition and keeps looping until the termination condition is met. The counter variable is managed by the context of the statements inside the curly braces. while(varname<11) { }

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While loop example <html> <head> <title>While loop example</title> <script language=“JavaScript”> var counter = 100; var numberlist = “”; while (counter > 0) { numberlist += “Number “ + counter + “<br>”; counter -= 10; } document.write(numberlist); </script> <body> … </body> </html>

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Do…while loop The do/while loop always executes statements in the loop in the first iteration of the loop. The termination condition is placed at the bottom of the loop. Syntax: do { statements; counter increment/decrement; } while (termination condition)

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Do…while example

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Array An Array contains a set of data represented by a single variable name. Arrays in JavaScript are represented by the Array Object, we need to “new Array()” to construct this object. The first element of the array is “Array[0]” until the last one Array[i-1]. E.g. myArray = new Array(5) We have myArray[0,1,2,3,4].

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Array Example <script type=“text/javascript”> Car = new Array(3); Car[0] = “Ford”; Car[1] = “Toyota”; Car[2] = “Honda”; document.write(Car[0] + “<br>”); document.write(Car[1] + “<br>”); document.write(Car[2] + “<br>”); </script>

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Array You can also declare arrays with variable length. arrayName = new Array(); Length = 0, allows automatic extension of the length. Car[9] = “Ford”; Car[99] = “Honda”;

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Events The most exciting JavaScript-powered pages are dynamic. Which means they perform various actions as your visitor interacts with them(moving his mouse, typing in the text, clicking things, and so on). Events are notifications that an HTML element sends out when specific things happen An HTML event can be something the browser does, or something a user does. Examples An HTML web page has finished loading An HTML input field was changed An HTML button was clicked